Pumps, fans, and compressors can be used in industrial and municipal applications. As pump, fan, and compressor applications consume a notable amount of electrical energy, they also hold energy savings potential.
A variable which may have an effect on the savings potential in these applications is the static head of the system. The static head represents a pressure difference in the form of a vertical fluid column height which a fluid transfer device has to overcome in order to produce flow.
Information on the system static head can be used, for example, in energy audits, energy-efficiency-optimizing speed control of fluid transfer systems, and determination of rotational speed limits for the device.
The static head can be a parameter for defining a minimum possible energy consumption of a fluid transfer device, such as a pump, a fan, or a compressor. For example, a system-specific energy consumption Es (kWh/m3) of a fluid transfer system can be defined as follows:
                              E          s                =                              ρ            ⁢                                                  ⁢            g            ⁢                                                  ⁢                          (                                                H                  st                                +                                  H                  dyn                                            )                                                          η              dt                        ⁢                          η              p                                                          (        1        )            where ρ is the fluid density, g is the acceleration due to gravity, Hst is the static head, Hdyn is a system dynamic head caused by flow losses, ηdt is the drive train efficiency, and ηp is the device efficiency. Equation 1 shows the direct effect that Hst can have on the system specific-energy consumption Es.
Energy efficiency of a fluid transfer system operation can be improved by driving the fluid transfer device of the fluid transfer system at a selected rotational speed with the smallest possible specific energy consumption, if allowed by the surrounding process. The static head can affect the feasibility of a speed control method for a fluid transfer device, since the static head in the system curve can set a practical limit for the minimum or selected applicable rotational speed.
The static head of a fluid transfer system can be determined by additional measurements. However, for example, sensors for the additional measurements may decrease cost-effectiveness of the system.
The static head of a fluid transfer system can also be determined without additional measurements by identifying the system curve parameters with a frequency converter. This method, however, can have relatively high computational needs since it uses the least squares method for determining the system curve parameters.